Context: Component
Goals: Systems will be designed such that the capacity of the system can be increased or decreased by adding or removing hardware or software components.
Rationale: If the availability and performance requirements of a system are sufficiently critical, the system must have the capability of cost effectively matching the system capacity to system load.
Requirement: Additions to, or subtractions from the capacity of a system shall not cause user detectable loss of business functionality for an elapsed time more than Metric.
Metric:
Level A:
A1. Adding and removing capacity results in no user detectable loss of business functionality
Level B:
This Level Intentionally Left Blank
Level C:
This Level Intentionally Left Blank
Level D:
D1. Adding and removing capacity results in a user detectable loss of business functionality no longer than Maintainability-Component Non-Functional Requirement, Level B.
Scale: Availability: Duration, elapsed time
Stakeholders: System Managers, Operations Staff
Implications: If this requirement is not met, the organization will incur increased cost associated with adding capacity and meeting peak demands. Additionally, if this requirement is not met, the system is subject to extended application outages during capacity upgrades.
Applicability: See Enterprise Requirements Framework
Tags: Scalability, Capacity,
Status: Draft, Guidance
Author: <Author>
Revision: <Revision>
Note:
Scalability requirements describe the ability to add and remove capacity to the system without affecting the availability of the system, while maximizing maintainability and constraining costs.
Incorporates the traditional concept of 'Horizontal Scalability', load balancing and dynamic capacity management. Assures that systems are compatible with cloud technologies.
The intent of this NFR is to force systems into a horizontally scalable architecture, and to limit or prohibit designs that depend on large-scale hardware upgrades to scale to additional capacity. I.E systems must be designed to scale out, not scale up.
For more information, see NFR Summary
